Al-Shabaab militants are suspected of being behind the ambush in Mandera CountyGetty Images

Kenyan Muslims travelling on a bus ambushed by Islamist militants protected Christian passengers by refusing to split into two groups based on their religion, survivors have said. At least two people were killed in the ambush in Mandera County, near the border with Somalia and Ethiopia.

Somalian terror group al-Shabaab is suspected of being behind the attack, although it has not claimed responsibility.

Who are the Al-Shabaab militants?

Al-Shabaab, which means "The Youth", is a Somali terror group affiliated to al-Qaeda.

An off-shoot of the Islamic Courts Union – a rival administration to the Transitional Federal Government in Somalia – Al-Shabaab aims to overthrow the Somali government and impose its own version of Islam in the country.

It controlled Mogadishu and the southern region of Somalia from 2006 until 2011, when it was defeated by African Union peacekeepers.

Witnesses told AP that Muslims also helped the other passengers change into Islamic clothes to disguise their identities. In a previous attack blamed on Shabaab in December 2014, witnesses said the terrorists had separated Muslims from non-Muslims before shooting at least 36 people dead in Koromei, in Mandera.

The bus, with 60 people on board, was travelling from the capital Nairobi. It was stopped at Papa City by the armed militants, who ordered the passengers to disembark and divide into two groups, one for Muslims and the other for non-Muslims.

One non-Muslim tried to flee and was shot dead. Witnesses said the other non-Muslims were saved after one of the passengers alleged a truck full of police officers escorting the bus was approaching.

The extremists then ambushed a truck on the same road and asked the driver whether he had seen a vehicle with police officers. They shot the passenger, a non-Muslim off-duty police officer, and then decided to leave.

Shabaab often targets Kenya in retaliation for the Linda Nchi military operation, which saw the deployment of Kenyan troops to Somalia to drive out the militants in 2011.

In one of its deadliest attacks in Kenya, Shabaab killed 148 people during an assault on a university college in Garissa in April. When the militants claimed responsibility for the attack, they said that the people were murdered as the university "is on Muslim land colonised by non-Muslims".

At least 67 people were killed during a four-day siege at Westgate shopping mall in Nairobi in 2013. Al-Shabaab later took responsibility for the bloody attack.